Memory package

ABSTRACT

A memory chip package with a controller die on a first side of a printed circuit board and a memory die on a second side of the same printed circuit board. The memory chip package is integrated into a microprocessor controlled device or alternatively is integrated into a portable memory card.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 10/921,549,filed Aug. 18, 2004, which in turn is a continuation of application Ser.No. 10/649,312, filed Aug. 26, 2003, now U.S. Pat. No. 6,797,538, whichin turn is a divisional of application Ser. No. 10/112,968, filed Mar.28, 2002, now U.S. Pat. No. 6,639,309, which application is incorporatedherein in its entirety by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to semiconductor memory chip packaging,and in particular to stacked multiple memory chip packages.

2. Discussion of the Related Art

Due to size limitations of printed circuit boards (PCB), only a finitenumber of packaged chips can be placed on a PCB. As the complexity ofapplications increases, a greater number of chips are needed on the PCBto implement the necessary functions, which would require larger sizePCBs. However, it is also desirable to decrease the size of PCBs anddevices containing PCBs. One method of achieving both these objectivesis to increase the number of chips in a package, such as by stacking thechips, without increasing the planar area of the package. Stacking thechips can result in a smaller overall package footprint. However,stacking the chips directly on top of each other has its own drawbacks.When a chip is stacked upon a base chip, the base chip can be damaged inthe process. Many different types of damage can occur including damageto the leads. Furthermore, while the footprint may be reduced, theheight or aspect ratio is increased with the stacked chips.

SUMMARY OF THE INVENTION

Therefore, a need has arisen for a semiconductor chip package andpackaging method that meets these challenges. One aspect of theinvention is a memory package with a controller die on one side of aprinted circuit board and a memory die on another side. Another aspectinvolves integrating the memory package into a memory card with optionaladditional memory. Yet another aspect is a microprocessor controlleddevice integrating the memory package with the controller die on oneside of a printed circuit board and a memory die on the other side.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of multiple chip packages beforefabrication.

FIGS. 2 a-2 c are cross sections of a chip package 100 at various stagesof the fabrication process.

FIG. 3 is a cross section of chip package 300.

FIG. 4 is a cross section of chip package 400.

FIG. 5 is a schematic diagram of a chip package such as chip package100, 300, or 400.

FIG. 6 is a schematic diagram of a device integrating a chip packagesuch as chip package 100, 300, or 400.

FIG. 7 a is a plan view of a first side of a memory card 500 formed withthe memory chip package, another embodiment of the present invention.

FIG. 7 b is a plan view of a second side of the memory card 500 shown inFIG. 7 a.

FIG. 7 c is a cross section of memory card 500 shown in FIGS. 7 a and 7b.

FIG. 7 d is a cross section of memory card 500 shown in FIGS. 7 a and 7b.

FIG. 7 e is a cross section of memory card 500 shown in FIGS. 7 a and 7b.

FIG. 8 is a plan view of a memory card 600 formed with the memory chippackage, another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Memory chip packages that include a controller may be utilized in manydiverse applications. In all of the applications space is at a premium,and long term reliability is essential. The packages can be integratedinto complex embedded systems such as cell phones or any microprocessorcontrolled device, or the packages can also be used to make memorycards. A memory package according to the present invention generallycomprises a memory die and a controller die to organize communicationwith external devices and to control the reading and writing of data toand from the memory locations of the memory die. The controller thussimplifies the reading and writing of data to the memory cells so that adevice that integrates the package need only communicate with thecontroller with simple commands and need not directly access the memorycells with much more complicated signals. The functionality of thecontroller die and memory die will be discussed in greater detail laterwith regard to FIGS. 5 and 6.

The memory capacity per die is increasing rapidly. One die may have acapacity of anywhere from a few kilobytes to several megabytes. Someembedded applications may not require a high capacity whereas thestorage of digital audio and images requires as high a density as can beachieved. The present package can be configured in many differentcapacities suitable for many different applications. The memory may beread only memory (ROM), random access memory (RAM), or flash type RAM.Currently the maximum capacity for a single flash memory die is roughly64 megabytes. By the time this patent issues the same size die ispredicted to hold over 256 megabytes of flash memory with an overallpackage size of 13×17 mm with a thickness of less than one mm.

Piggybacking the controller die on top of the memory die is known. Suchan arrangement may lead to damage of either one or both of the die.Mounting the memory die on an opposite side of a printed circuit boardavoids this potential damage, thus reducing the number of packages thatmust be scrapped after testing, and enhancing the long term reliabilityof those packages that pass the initial burn in test but may potentiallyfail during the lifetime of the product.

FIG. 1 illustrates an initial step in the formation of a group of memorypackages. Two printed circuit boards 110 and 112 are laminated togetherbefore the assembly is saw cut into individual packages. The individualpackages may be saw cut or sheared apart. Two of these packages 100 aand 100 b are labeled in FIG. 1. Within each of the PCB's are a numberof conductive layers that are used to connect various components mountedon the PCB's to form a myriad of circuits. Printed circuit board (PCB)112 has a group of rectangular or square holes 118 formed within it.These holes may be machined out of PCB 112 in any number of ways, or PCB112 may be pre-formed with the holes.

FIGS. 2 a-2 c illustrate a cross section of the various stages of anindividual package 100, for instance 100 a or 100 b of FIG. 1, duringfabrication. Controller die 120 is mounted to PCB 110 within therectangular hole of PCB 112, as shown in FIG. 2 a. Alternatively, onePCB can be used in place of the two PCBs 110 and 112. In this case, PCB110 would have a thickness approximately equal to both PCB 110 and 112and a central recess for the controller would be formed within PCB 110.This central recess may be mechanically formed by a process such asmilling or may be formed by selectively laminating layers withpre-formed cutouts.

FIG. 2 b shows vias 128 that have been made through PCB 110 and PCB 112to connect components on the top and bottom sides of the package 100.Bond wires 124 connect controller die 120 to vias 128. After the bondwires have been formed controller die 120 is encapsulated withencapsulent 132. Encapsulent 132 can be any substance well known in theart such as bakelite, phenolic, epoxy or a thermal setting compound.

In FIG. 2 c, memory die 144 is mounted to the topside of PCB 110. Bondwires 148 connect the bond pads of memory die 144 with vias 128, some ofwhich are intern connected to solder balls 156. Solder balls 156 areconnected to vias 128 in order to later mount package 116 a to anothercircuit board. Memory die 144 and bond wires 148 are then encapsulatedwith any well known material to form encapsulent 152. Encapsulent 152has a flat top and square edges as it was one of multiple packages cutfrom a circuit board. However, the packages may be individually formedin which case the encapsulent 152 would taper down towards PCB 110 nearthe edges of package 100. Memory package 100 is about 0.7 mm thickwithout solder balls 156 and slightly less than one mm thick with solderballs 156. Circuit traces within PCB 110 can connect memory die 144 tocontroller die 120 through additional vias and bond wires (not shown),or can connect to flush mount contacts on the opposite or circuit boardside of memory die 144 and controller die 120.

As an alternative to encapsulating the top and bottom sides (memory die144 and controller die 120) in separate steps, the entire package can betransfer molded at the same time after the die have been mounted.

FIG. 3 illustrates a cross section of a memory package according to asecond embodiment of the present invention. Memory package 300 issimilar to memory package 100 described above except that memory die 144is flip chip bonded to the top of PCB 110 and thus bond wires connectingthe memory die to the circuit board are eliminated, thereby reducing theheight of package 300 relative to package 100. The bonding pads orterminals of memory die 144 are conductively connected through vias andconductive layers of PCB 110 and 112 to controller die 120. Package 300is shown without any encapsulent on the top side of PCB 110 and memorydie 144, however, an encapsulent may be applied.

FIG. 4 illustrates a cross section of a memory package according to athird embodiment of the present invention. Memory package 400 is similarto memory package 300 but both memory die 144 and controller die 120 areflip chip bonded to PCB 110. Thus, conductive layers of PCB 110 are usedto interconnect controller die 120 to memory die 144. Because no bondwires are present, package 400 has a very low aspect ratio, a veryimportant feature for today's portable devices.

FIG. 5 is an electrical schematic of any of the chip packages describedthus far, for instance controller die 120 and memory die 144 of chippackage 100. The memory controller 100 includes appropriate systeminterface circuits 43 for interfacing with a computer system bus 15, acontroller microprocessor 45, volatile buffer memory 47 for temporarilystoring data being written to or read from the memory, and control logiccircuitry 49. These circuit units are interconnected and under thecontrol of the microprocessor 45. The EEPROM banks within memory die 144are connected to the controller logic 49 over circuits including datalines 51, address-lines 53 and control and status lines 55. Furtherdetails of the system illustrated in FIG. 5 can be had by reference toU.S. Pat. No. 6,081,447 to Lofgren et al., entitled “Wear LevelingTechniques for Flash EEPROM Systems,” and to PCT Patent No. WO 01/61703A2 of the Sandisk Corporation, entitled “Flash EEPROM System withSimultaneous Multiple Data Sector Programming and Storage of PhysicalBlock Characteristics in Other Designated Blocks,” both of which arehereby incorporated by this reference in their entirety. U.S. Pat. No.5,663,901 to Wallace et al., entitled “Computer Memory Cards Using FlashEEPROM Integrated Circuit Chips and Memory-Controller Systems,” alsodescribes the functionality of the controller in further detail, and ishereby incorporated by this reference in its entirety.

The EEPROM cells in memory die 144 can have either a NOR or NANDstructure. For further information on the NAND structure andconfiguration please refer to U.S. Pat. No. 6,046,935 to Takeuchi et al.entitled “Semiconductor Device and Memory System,” which is herebyincorporated in its entirety by this reference.

Depending on whether a NAND or NOR structure is employed, the arrays ofrows and columns will differ and the data lines 51, address lines 53,and control and status lines 55 will have different configurations.However, generally speaking, data to be read or written into thespecific memory cells will be transferred over data lines 51. Theaddress of those specific memory cells will be transferred over addresslines 53, and the status of the specifically addressed cells istransferred over control and status lines 55. For instance, the statusof a memory cell after a write (program) operation may checked overcontrol and status lines 55. These lines 51, 53, and 55 correspond tothe bond wires 124 and vias 128 in the chip package 100 illustrated inFIGS. 2 a-c, or to a combination of bond wires 124, vias 128, andcircuit traces 130 in the flip chip packages 300 and 400 illustrated inFIGS. 3 and 4. The system interface circuits include solder balls 156and bond wires 144, and may also include other bond wires andinterconnects.

Any of the memory packages described above can be integrated as acomponent into any type of device 64 needing a thin memory package. Aschematic of a typical embedded application of which a memory chippackage of the present invention may be integrated is shown in FIG. 6.For instance, memory chip package 100 is shown connected by anelectrical bus to input-output devices 60, RAM memory 62, andmicroprocessor 64. Device 64 may be any smart device such as a personalcomputer, portable organizer or music player, cell phone or any otherdevice needing memory for storage of data.

The package can also be used in a memory card. FIG. 7 a illustrates thefirst face of a memory card 500 formed from memory package 510 andoptional passive devices 520 mounted on PCB 505. PCB 505 is amulti-layer circuit board and circuit traces are formed in a conductivelayer (not shown) of PCB 505 to interconnect the memory package 510 andany other electronic components to contacts 525. The passive devicesare, for example, charge pumping capacitors used to convert a suppliedvoltage to a larger voltage required to modify the flash memory of thememory package 510 or any other memory that may be integrated into card500. Passive devices 520 may not be present as separate components ofmemory card 500 if they are integrated into memory package 510. If thisis the case, then memory package 510 would contain all the circuitcomponents of memory card 500 aside from electrical circuit traces, aportion of which can be used as test contacts, and contacts 525 on theopposite face of the memory card 500 shown in FIG. 7 b. FIG. 7 c is across section of memory card 500 showing memory package 510 and passivedevices 520 upon PCB 505. FIG. 7 d is a cross section illustrating aplastic cover 535 extending over the face and sides of the memory cardhaving package 510 and optional passive devices 520. FIG. 7 eillustrates an embodiment of memory card 500 wherein the cover 535extends all around the memory card. In this case, cover 535 includescutouts or voids where contacts 525 are located on the opposite face ofPCB 505.

For further information on memory cards and packages, see U.S. Pat. No.6,040,622, issued Mar. 21, 2000, by Robert F. Wallace, entitled“Semiconductor Package Using Terminals Formed on a Conductive Layer of aCircuit Board,” which is hereby incorporated by this reference in itsentirety.

FIG. 8 illustrates the first face of memory card 600 comprising memorypackage 510 and an additional memory die 530 mounted to the circuitboard. Memory die 530 may be any type of memory and provides additionalstorage capacity for memory card 600. The controller present in memorypackage 510 will be used to access the information in additional memorydie 530.

While particular embodiments of the present invention and theiradvantages have been shown and described, it should be understood thatvarious changes, substitutions, and alterations can be made thereinwithout departing from the spirit and scope of the invention as definedby the appended Claims.

1. A method of making a memory chip package, the method comprising:providing a circuit board having first and second opposing faces;attaching a FLASH EEPROM having memory cells to the first face of thecircuit board; attaching a controller having a control logic to thesecond face of the circuit board, and configuring the controller to readand write data to the memory cells on the first face; and providing datalines within the circuit board connecting the controller die to theEEPROM, the data lines operable to transfer data to and from the memorycells.
 2. A method of making a microprocessor controlled device, themethod comprising: providing a memory chip package comprising a circuitboard having a first and second face; attaching a controller die to thefirst face of the circuit board; attaching a memory die to the secondface of the circuit board; providing a system bus; providing one or moreinput-output devices electrically coupled to the system bus and thememory chip package; providing random access memory electrically coupledto the system bus and the memory chip package; and providing amicroprocessor.
 3. A method of making a memory card, the methodcomprising: providing a first circuit board having a first and secondface; exposing a set of contacts on the second face of the first circuitboard on a face of the memory card; attaching a memory package to thefirst face of the circuit board, the memory package comprising a secondcircuit board, a controller die attached to a first face of the secondcircuit board, and a memory die attached to a second face of the secondcircuit board.
 4. The method of claim 3 further comprising formingcontrol and status lines connecting the memory die to the controllerdie, the control and status lines operable to monitor the state of thememory cells over the control and status lines.
 5. A method of making amemory card, comprising: attaching a plurality of memory die to thefirst face of a first circuit board; attaching a plurality of controllerdie to the second face of the first circuit board, each controller diepositioned beneath a memory die; laminating the second face of the firstcircuit board to a first face of a second circuit board having aplurality of recesses such that the plurality of controller die fitwithin the plurality of recesses; forming vias in the first and secondcircuit boards connecting the controller die to beneath the memory dieto the memory die to form a plurality of memory packages; cutting thefirst and second circuit boards between the plurality of memory packagesto form individual memory packages; and placing an individual memorypackage into a memory card body such that a set of contacts on one ofthe first or second circuit boards is exposed from the body in order tomake contact with a memory card receptacle.
 6. The method of claim 5,wherein the memory die is of a NAND flash architecture.